The present invention relates to a magnetic head which is used for recording and/or reproducing data on and/or from a magnetic recording medium having a high coercive force such as so-called metal tape.
For example, in the magnetic recording and/or reproducing apparatus such as VCR (video cassette recorder), efforts have been made to record informational signals having a short wave length to provide a high resolution picture. In associated with this, magnetic recording media having a high coercive force such as so-called metal tape using ferromagnetic metal powders such as magnetic powders or vacuum deposited tape in which a ferromagnetic metal material is directly deposited on a base film have been used.
On the other hand, research and development in the field of magnetic head has been made to cope with the advance in the magnetic recording medium. A magnetic head in which a thin magnetic metal film having a high saturation magnetic flux density is adjacent to a magnetic gap which is preferable for the high coercive force magnetic recording medium has been developed. Such a magnetic head comprises a pair of magnetic core halves each including a substrate which is generally made of an oxide magnetic material or non-magnetic material. Thin magnetic metal films are formed on the facing surfaces of the substrates. The magnetic core halves are integrally bonded to each other with fused glass so that a gap film is disposed in a magnetic gap formed between the thin magnetic metal films. Although the thin magnetic metal film adjacent to the magnetic gap is generally a single layer, a laminated film including a multiple of thin magnetic metal films having non-magnetic films interposed therebetween to provide a high output and a broader band has also been proposed.
In the magnetic head having a thin magnetic metal film adjacent to the magnetic gap, it is preferable to continuously extend the thin magnetic metal film from a magnetic recording medium sliding surface of the head to the rear side thereof along a winding groove which is notched in the substrate. If such a continuous thin magnetic metal film is formed, a closed magnetic path is formed by only the thin magnetic metal film. Accordingly, enhancement of the reproduced output can be achieved. In such type magnetic head, the length of the facing portions of the thin magnetic metal films which sandwich a gap film therebetween in a depth direction is defined as the depth of the magnetic gap.
The width of the thin magnetic metal film exposed on the magnetic recording medium sliding surface in a film thickness direction will be gradually widened from a position passing the notching start position of the winding groove provided in the substrate in the side of the magnetic gap due to wearing of the magnetic recording medium sliding surface by the sliding contact with a magnetic recording medium. In other words, the area of the thin magnetic metal film on the magnetic recording medium sliding surface will be increased. After the area of the thin magnetic metal film exposed on the magnetic recording medium sliding surface has been increased, mainly the thin magnetic metal film is worn instead of the substrate on the recording medium sliding surface. Wearing of the thin magnetic metal film is more remarkable than that of the substrate. Therefore, the contour of the magnetic recording medium sliding surface changes with the lapse of use period of time, so that contact of the medium sliding surface of the magnetic head with the magnetic recording medium can not be assured.
In particular, in the magnetic head having a laminated thin magnetic metal film, non-magnetic films interposed between the thin magnetic metal films formed on the winding groove will be exposed on the magnetic recording medium sliding surface in parallel with the magnetic gap after the notching start position of the winding groove whether or not the thin magnetic metal film exposed on the magnetic recording medium sliding surface at the initial phase before use is parallel with the magnetic gap. Since the non-magnetic films are in parallel with the magnetic gap, they function as so-called pseudo magnetic gap which may cause noise in a reproduced signal.